Exam #1 Flashcards
(121 cards)
1
Q
Stars and other great celestial objects appear to lie on a great __________ surrounding earth
A
celestial sphere
2
Q
We divide the celestial sphere into ______ with well defined borders.
A
constellations
3
Q
From any location on Earth we see half the celestial sphere at any one time as the dome of our _______
A
local sky
4
Q
What is the boundary between Earth and sky?
A
The Horizon
5
Q
The _____ is the point directly overhead of you in the celestial sphere.
A
zenith
6
Q
The ______ runs from due south to due north through the zenith.
A
meridian.
7
Q
Why do stars rise and set?
A
Because the earth is rotating and hence stars appear to circle around us.
8
Q
A star whose complete circle lies above our horizon is said to be a __________.
A
circumpolar star
9
Q
Why do the constellations we see depend on latitude and time of year? What about longitude?
A
The visible constellations vary with time of year because our night sky lies in different directions in space as we orbit the Sun. The constellations vary with latitude because your latitude determines the orientation of your horizon relative to the celestial sphere. The sky does not vary with longitude.
10
Q
What causes the seasons?
A
The tilt of Earth’s axis. The tilt of Earth’s axis never changes, so sunlight hits certain parts of Earth more directly at certain points in our planets rotation.
11
Q
What is the difference between a solar and a lunar eclipse?
A
A lunar eclipse is when Earth’s shadow falls on the moon, while a solar eclipse is when the Moon blocks our view of the Sun. We do not see an eclipse at every new and full Moon because the Moon’s orbit is slightly inclined to the ecliptic plane.
12
Q
What direction do the planets move, relative to the stars, over the course of a year?
A
eastward
13
Q
For weeks or even months, planets sometimes appear to reverse course during periods of _______.
A
apparent retrograde motion.
14
Q
What causes apparent retrograde motion?
A
apparent retrograde motion occurs when Earth passes (or is passed by) another planet on its orbit around the Sun. As you can imagine, this perplexed ancient philosophers who were yet to adopt the heliocentric model of the solar system.
15
Q
Why did ancient Greeks reject the real model of planetary motion?
A
They could not detect stellar parallax (slight apparent shifts in stellar positions over the course of the year). To most Greeks, the idea that the stars could be so far away as to make parallax undetectable was unlikely, even though this actually was the case.
16
Q
How did the Greeks explain planetary motion?
A
the Ptolemaic model, which explained retrograde motion by having each planet move on a small circle whose center moves around the earth in a larger circle.
17
Q
How did Copernicus, Tycho, and Kepler challenge the Earth-centered model?
A
Copernicus created a Sun-centered model of the solar system designed to replace the Ptolemaic
model, but it was no more accurate than Ptolemy’s because Copernicus still used perfect circles.
Tycho’s accurate, naked-eye observations provided the data needed to improve on Copernicus’s
model. Kepler developed a model of planetary motion that fit Tycho’s data.
18
Q
What is Kepler’s first law of motion?
A
(1) The orbit of each planet is an ellipse with the Sun at one focus.
19
Q
What is Kepler’s second law of motion?
A
(2) A planet moves faster in the part of its orbit nearer the Sun and slower when farther from the Sun, sweeping out equal areas in equal times.
20
Q
What is Kepler’s third law of motion?
A
(3) More distant planets orbit the sun at slower average speeds, obeying the mathematical relationship p^2 = a^3.
21
Q
What was my working definition of science?
A
A process of gaining knowledge/understanding through observation/experimentation of the physical world and through our reason.
22
Q
What is the primary way of knowing in science?
A
Observation/Experimentation
23
Q
According to Richard Feynman, what is the test of all scientific truth?
A
Experiment
24
Q
In what ways is science different than a list of all the scientific facts discovered?
A
Science is more than just a collection of facts! First, facts without understanding cannot constitute a science (Henry Poincaré). Second, science is arguably more a way of thinking than it is a body of knowledge (Carl Sagan, William Bragg). Science is a way of understanding facts–it is a house, not just the stones.
25
In what ways is science different than technology?
Planck thought that genuine scientific knowledge and discovery have only been achieved by those who sought them for their own sake “without any practical purpose in view whatsoever.”
26
Be able to list several strengths of science.
Stupendous explanatory power, very well-tested theories, wonderful technology, frees from the fear of superstition, and power over nature are all strengths of science.
27
Be able to give at least 3 possible limits of science as discussed in class.
Scientific knowledge is contingent knowledge (any physical theory is always a hypothesis: you can never prove it - Stephen Hawking); science cannot make moral judgements (science is amoral); science cannot make aesthetic judgements; science does not tell you how to use scientific knowledge; science can tell the “how” but not the “why”.
28
What is scientism?
Excessive belief in scientific knowledge or techniques; the belief that science, modeled on the natural sciences, is the only source of real knowledge.
29
What is materialism/physicalism?
Materialism: holds that matter is the fundamental substance in nature, and that all phenomena, including mental phenomena and consciousness, are results of material interactions.
30
Who decomposed white light using a prism and subsequently did a series of experiments in c. 1670?
Isaac Newton
31
Describe the phenomenon measured in the “Roemer Delay”?
Conclusion: light has a finite speed, and we can measure it.
At two different points in Earth's orbit, Jupiter's moon was studied at the same point but on two successive orbits. From this, the speed of light was deduced.
32
Who discovered the nature of light in the 1870’s?
James Clerk Maxwell
33
What two phenomena did he “unite” to show the true nature of light?
Electricity and Magnetism
34
Be able to list the major components of the EM spectrum, and order them based on wavelength
and frequency.
Gamma Ray, Ultra-Violet Ray, Visible, Infrared, Microwave, Radio
(Remember, shorter wavelength means higher frequency)
35
Be able to order the colors red and violet based on wavelength and frequency.
From greater to lesser frequency (i.e. lesser to greater wavelength): violet, indigo, blue, green, yellow, orange, and red.
36
Which has longer wavelength, red or violet?
Red has the longer wavelength and lesser frequency. It is closer to infrared light, while violet is closer to ultraviolet light, with greater frequency and smaller wavelengths.
37
Which has higher frequency, red or violet?
Violet has higher frequency (and shorter wavelength).
38
What part of the spectrum is the Hubble Space Telescope sensitive to?
Visible Light.
39
Besides visible light, what other part of the EM spectrum can ground-based telescopes be used
to observe?
Radio Waves
40
True or False: All stars are white.
False.
41
Why do stars generally all appear white to the unaided eye?
Because the cones in our eyes (that detect light) aren’t very sensitive. If a light is too dim (like the stars, which are so far away) we perceive it as white.
42
Which is hotter, something glowing white or something glowing red?
Something glowing white.
43
Which is hotter, something glowing orange or something glowing red?
Something glowing orange. Red is cooler to blue and white, which are the hottest stars.
44
Which is hotter, lightning or a wood fire?
Lightning.
45
Which is hotter, lightning or lava?
Lightning.
46
What part of the EM spectrum do you sense as heat?
Infrared light/radiation
47
What’s the difference in the angle of approach of the sun towards the horizon if you are watching the sunset in the northern hemisphere, southern hemisphere, or equator?
In the northern hemisphere: the sunset “grazes to the right”; in the southern hemisphere: the sun “sets” to the left; on the equator: the sun sets straight down.
48
Compared to the direction of the earth’s revolution around the sun, do the following rotate in
the same or different direction: Rotation of Sun, Rotation of Earth, Rotation of Moon, Orbit of Moon
All rotate in the same direction.
49
Know the approximate ratios of the diameters of the moon/earth, moon/sun, and earth/sun
Earth/ Moon: 3.7/1
Sun/ Earth: 109/1
Sun/ Moon: 400/1
50
How many light-minutes is the earth from the sun?
8.3 light-minutes
51
How many light-seconds is the moon from the earth?
1.25 light- seconds
52
What is the ratio of the earth’s orbital radius around the sun to the moon’s orbital radius around
Earth?
Earth: Moon = 389:1
53
What is the approximate ratio of the moon’s orbital radius to the earth’s diameter?
30.2:1
54
What is the approximate ratio of the earth’s orbital radius to the sun’s diameter?
108:1
55
Have humans ever seen the back side of the moon?
Humans did not see the dark side of the moon until 1959; in 1959, the Soviet Union used the Luna 3 space Probe to take photos; in 1968, the Apollo 8 sent the first humans to physically see the dark side of the moon.
56
When you look at objects in the sky, you can see/measure angle, but not actual size/diameter.
You should know how many degrees are in a circle, how many arcminutes in a degree, how many arcseconds in an arcminute.
There are 360 degrees in a circle
There are 21,000 arcminutes in a circle
There are 1,296,000 arcseconds in 21,000 arcminutes
In other words, there are 60 arcminutes in a degree, and 60 arcseconds in an arcminute.
57
What is the approximate angular size of the sun and moon in the sky?
The Sun is about 32 arcminutes. The minimum is 31.6 arcminutes, while the maximum is 32.7 arcminutes.
The Moon is about 31 arcminutes. Its minimum is 29.43 arcminutes, and its maximum is 33.5 arcminutes.
58
Which planet can have the largest angular size in the sky?
Venus at 66 arcseconds.
59
What are the names of the two angles used to define the location of an object on the earth’s
Surface?
Latitude and Longitude.
60
Which is measured from the equator, and which is measured from the Prime Meridian?
Latitude is measured from the equator, while longitude is measured from the Prime Meridian.
61
What is at 90 degrees N latitude? What is at 90 degrees S latitude?
The North Celestial Pole is at 90 degrees north latitude. The south celestial pole is at 90 degrees south latitude.
62
Through what observatory does the Prime Meridian pass?
The Royal Observatory, Greenwich, England
63
What are the names of the two angles used to define the location of an object in the sky?
The altitude and azimuth.
64
What is the “zenith” and the “celestial meridian”?
The Zenith is the point directly overhead with has an altitude of 90 degrees. The Celestial Meridian is a circle passing through the celestial poles and the zenith of a given place on the earth's surface.
65
If you are in the northern hemisphere, looking at the north star, are the stars rotating clockwise
or counterclockwise?
The stars are rotating counterclockwise. The Earth rotates from west to east, making the celestial sphere appear to rotate around us from east to west.
66
What physical situation makes the north star the north star?
The north star (Polaris) is rather bright and located almost exactly at the north celestial pole, so the entire northern hemisphere rotates around it. There is no “south star” because no bright star in the southern hemisphere is located very close to the south celestial pole.
67
What is the rotation rate of stars in the sky in degrees per minute?
¼ degree/minute [full circle = 360 degrees, full rotation of earth = 24hrs]
68
Be able to identify how long a star trail exposure was given that you know the angular length of
the trail, and vice versa
Example: if given a 3 degrees of rotation
3 degrees / ¼ degree per minute = 12 minute exposure
Example: if given 12 minute exposure, 1/4 degree per minute * 12 = 3 degrees.
69
Does the sun have the same rotation rate in the sky as do the stars? What about the moon? What about the planets?
The moon, sun, and planets have additional sky motions beside the motion due to Earth’s Rotation
Moon = 12 degrees/day
Sun = 1 degree/day
70
If you are at a latitude of 42 degrees north, at what angle above the horizon is the north star?
42 degrees (your Geographical Latitude = Height of North Star above horizon)
71
What if you are on the equator?
0 degrees.
72
What is an occultation?
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.
73
Why is the moon moving relative to the background stars? About how long does it take for the
moon to make once complete circuit relative to the background stars?
Because of Earth’s rotation paired with its orbit. (simply put, the moon orbits the stars do not). Moon takes about a month (27.3 days)
74
Is the moon’s orbit circular? Is it in the same plane as the earth’s orbit around the sun?
The Moon’s orbit is elliptical. It is not in the same plane as the earth’s orbit around the sun.
75
What is the physical difference between a sidereal month and a synodic month?
The Earth is constantly moving along its orbit about the Sun, the Moon must travel slightly more than 360° to get from one new moon to the next. Thus, the synodic month, or lunar month, is longer than the sidereal month. A sidereal month lasts 27.3 days, while a synodic month lasts 29.5 days.
Sidereal = full circle (which won’t be phase to phase due to earth’s orbit around sun)
Synodic = new moon to new moon
76
What causes the phases of the moon?
Half the moon is always illuminated by the sun, but the portion of this illuminated half that we see from Earth depends on the moon’s position in its orbit
77
How do you know the moon’s rotational period and orbital period are the same?
The fact that we always see the same face of the Moon means that the moon must rotate once in the same amount of time that it takes to orbit Earth once
78
How many degrees does the sun move, relative to the background stars, per day? How many in
one year? What about the moon?
```
Sun = 1 degree/day, 360 degrees/year
Moon = 12 degrees /day (or 13.2)
```
79
What is the name of the sun’s path in the sky?
The ‘ecliptic’
80
What is it about the constellations of the zodiac that set them apart from all the other constellations?
The zodiac constellations are the ones along the ecliptic
81
What was the early Greek model of the universe?
Geocentric
| Heavenly bodies on multiple rigid rotating crystal spheres, centered on Earth
82
Which Greek put forward a heliocentric model of the universe?
Aristarchus of Samos
83
In the end, why did people try to hold on to spheres and uniform circular motion so much?
The idea of “heavenly perfection” -- according to this idea, heavenly objects could move only in perfect circles
Stellar parallax
84
Describe retrograde motion of a planet.
“Retrograde Motion”: motion that is backward compared to the norm. During retrograde motion, a planet reverses direction (when it moves westward, rather than the more common eastward) for a few weeks to months. This motion is a result of the fact that planets rotate along their orbits
85
Describe Ptolemy’s model of the universe. What is an epicycle?
Each planet moves on a small circle whose center moves around Earth on a larger circle
Epicycle = the smaller circle^
Deferent = larger circle
This explained retrograde motion while maintaining perfect circles, uniform motion, and predictability
Prograde and epigrade
86
Why were many epicycles introduced rather than accepting non-uniform motion of planets?
Because Ptolemy wanted to maintain the “heavenly perfection” idea
87
Why is Venus known as the morning/evening star? How was this explained in Ptolemy’s theory?
Because it is the last seen “star” near the rising sun
| Ptolemy would explain this by saying the center of Venus’s epicycle lies on the line between Earth and the Sun
88
Describe the Copernican theory of the universe
Heliocentric - Sun at center of universe, but still believed in the ancient belief that heavenly motion must occur in perfect circles
No more accurate and no less complex than the Ptolemaic model
89
Why did Copernicus put forward his theory?
Because he had discovered simple geometric relationships that strengthened his belief in the sun-centered idea. These allowed him to calculate each planet's orbital period and relative distance (compared to Earth’s distance) from the Sun
Scholars and the Church urged him to publish
90
Did Tycho Brahe’s more accurate data favor the Copernican model or the Ptolemaic model?
His data didn’t support either the Copernican model or the Ptolemaic model
Detected a supernova that seemed to cast doubt on Ptolemaic
But, he failed to detect stellar parallax, so he didn’t support Copernican model
Tycho Model: all the planets revolve about the sun, which in turn revolves about the Earth
91
What were some criticisms of the Copernican model?
Few were willing to throw out thousands of years of tradition for a new model that worked as poorly as the old one
92
With which model did Kepler initially sympathize?
Kepler initially sympathized with the Copernican model
93
Describe Kepler’s model.
Kepler found that Tycho’s data simply did not support perfectly circular orbits, so he abandoned this idea.
Planets orbit the sun, in ellipses, with the sun at one focus. Kepler’s Laws of Planetary Motion:
The orbit of each planet about the sun is an ellipse with the sun at one focus. A planet moves faster in the part of its orbit nearer the sun and slower when farther from the sun, sweeping out equal areas in equal times. More distant planets orbit the sun at lower average speeds, obeying the precise mathematical relationship p2 = a3 (‘p’ is the planet’s orbital period in years and ‘a’ is its average distance from the sun in astronomical units).
94
What observations of Galileo would argue against the Ptolemaic model?
Jupiter’s moons proved heavenly bodies can move against stars/planets/sun (orbiting Jupiter, not Earth)
Phases of Venus (proved it orbited Sun and not Earth)
95
Who wrote the Starry Messenger?
Galileo
96
Observations of what heavenly objects does Galileo discuss in the Starry Messenger?
Earth’s moon, Jupiter’s moon, and the Milky Way
97
Galileo discovered the moons of what planet?
Jupiter
98
How many moons of this planet did Galileo observe?
Four.
99
What idea about the surface of the moon did Galileo spend much of the discussion of the Starry
Messenger refuting?
That it is smooth
100
Who was the first person to actually have to navigate a craft to avoid landing on a lunar crater?
Neil Armstrong
101
What are the two cultures?
The “traditional culture” and the “scientists”
102
What is the refraction of light?
The effect when light is bent as it passes from one medium into another
103
According to the article, what was Newton most surprised about when he passed white light
through a prism?
That the shape of the light beam projected on the wall was oblong
104
What would you say was the main conclusion drawn by Newton from his experiment with light
as described in the article?
His main conclusion is that a color is simply its degree of refrangibility. Each color has their own distinct degree.
105
Describe in simple terms how a prism produces a spectrum of colored light
As light enters the prism, the different frequencies and wavelengths refract and fan out to separate from one another
106
Would you say the colors reside already in white light or does the prism impart these colors to
It?
They already reside in the white light -- the prism separates them
107
Why did Newton stick a pin in his eye?
He wanted to see if color was influenced by the eye or if it was entirely independent.
108
What is the equation relating speed of light, wavelength, and frequency?
speed = (frequency) x (wavelength)
109
What is the speed of light in vacuum (number and units)?
the speed of light is 3.00 x 10^8 m/s
| 1 nm = 10-9 m
110
What is the approximate temperature and to what part of the EM spectrum do each of these
correspond? Earth, Oven, Incandescent Lightbulb, Sun)
Earth: 300 K, infrared
Oven: 615 K, infrared
Incandescent Light Bulb: 3000 K, infrared
Sun: 5700 K, visible-blue
111
What are the approximate wavelengths of violet and red light?
Violet: 400 nm
| Red light: 650 nm
112
What part of the EM spectrum does your cellphone use (the name of this part of the spectrum)?
VHF (Very High Frequency). Radio/Microwaves Frequencies.
113
What is usually missing or defective in people who have red-green color-blindness?
“Those affected have difficulty with discriminating red and green hues due to the absence or mutation of the red or green retinal photoreceptors.” - wiki
114
What is the name of the Space Telescope that took the “Ultra Deep Field” image explored in lab?
Hubble Space Telescope
115
Which was greater: the number of thistles in the 5 gallon bucket, or the number of galaxies in the known universe?
Number of galaxies in the known universe
116
What kind of assumptions or approximations do scientists make to estimate the number of
galaxies in the known universe? How do these compare to the estimations and approximations
you made in the lab concerning thistle seeds?
They assume that each section of space holds approximately the same number of galaxies. We assumed that each thistle seed weighs approximately the same and occupies the same amount of space.
117
How do you calculate the volume of a cylinder?
V = 𝝿r2h
118
Approximately how many galaxies are in the known universe?
1.65x10^11 galaxies
119
Which Apollo mission was the first to land on the moon? (You found its landing location in lab)
Apollo 11
120
WWT zoomed in on the moon within seconds. In reality, about how long would it take you to
travel there? (How long did it take the Apollo astronauts to travel there?)
Three days
121
You explored the relative distances and brightnesses of three stars in the “belt” of what constellation?
Orion
